The present invention is directed to a method and apparatus for inspecting a procession of bottles for relative orientation and spacing. In particular, the invention is directed to method and apparatus for inspecting such bottles for "down" and "stuck" conditions.
The invention is especially important in inspecting for and ejecting "down" and "stuck" bottles at the "hot end" of a glass bottle manufacturing plant between the furnace and the lehr. The invention, however, is also important in inspecting for and ejecting "down" bottles at the "cold end" of the plant downstream of the lehr.
Typically, in a glass bottle manufacturing plant, the bottles are spaced uniformly from each other and arranged in a single file procession on a moving conveyor. The bottles are transported by the conveyor from the furnace to the lehr and then onto various inspection and handling stations. At the "hot end" of the plant, bottles which come into contact with each other may become "stuck" either in an upright or a tilted position. In addition, "down" bottles may be encountered which have fallen on their sides on the conveyor either at the "hot end" or "cold end" of the plant. "Down" and "stuck" bottles must be removed from the conveyor in order to avoid line jams, and contact with good ware, and to reduce processing time.
The heat and dirt encountered in a typical bottle manufacturing plant presents a hostile environment for inspecting a process for "down" and "stuck" bottles, especially by optical devices. Various non-optical devices have been proposed for performing the inspection. For example, U.S. Pat. No. 3,968,368 discloses a heat sensing device for inspecting a procession of hot glass bottles prior to entry in the lehr. The device employs four heat sensing probes rather than optics. The probes are laterally pre-positioned in pairs on upper and lower carriers. Detection of "down" and "stuck" bottles is based on a pre-selected pattern in which the bottles block the heat sensing probes.
Various optical devices have also been proposed for detecting "down" and "stuck" bottles. For example, in U.S. Pat. No. 4,354,865 issued Oct. 19, 1982, there is disclosed a system wherein an infra-red radiant energy source-sensor pair are disposed on opposite sides of a moving conveyor at an elevation such that the radiation beam is interrupted by all ware, whether normal, "down" or "stuck". The sensor produces an output pulse only when the beam is not interrupted. At each detection of a bottle, a one shot generates a pulse of predetermined duration. If the beam is interrupted by a "stuck" bottle or a "down" bottle for a time interval in excess of the duration of the one shot pulse, a logic gate triggers a delay one shot which controls a reject mechanism.
Optical devices have also been proposed for detecting the silhouette of bottles randomly spaced on a moving conveyor. For example, in U.S. Pat. No. 3,837,486 issued Sept. 24, 1974, there is disclosed a system wherein a pulse generator is locked to the moving conveyor so as to obtain a pulse train having a frequency proportional to conveyor speed. A radiation source-sensor pair is arranged at an inspection station so as to generate a "diameter" pulse proportional to the time required by a bottle to transverse the station. The pulse generator pulses are counted within the "diameter" pulse and compared to preset minimum and maximum thresholds. If a count falls between the thresholds, the bottle is accepted. Otherwise, a reject mechanism is operated to remove the bottle from the conveyor.
Heretofore, no optical inspection device has been proposed for detecting "down" and "stuck" bottles based on a comparison to thresholds which automatically vary in proportion to variations in the average dimension of acceptable bottles. Moreover, no optical inspection device has been proposed wherein bottles which are "stuck" upright are detected based on the same sensor signal employed to detect "down" bottles and bottles which are "stuck" and tilted.
An advantage of the invention is that only a single sensor signal is needed to detect all "down" and "stuck" bottles.
A further advantage of the invention is that the detection scheme is substantially insensitive to degrading conditions typically encountered in the bottle manufacturing plant such as wide fluctuations in ambient light, extreme dirt, heat, etc.
A further advangtage of the invention is that the detection of "down" and "stuck" bottles is independent of the overall bottle shape and automatically compensates for changes in conveyor speed as well as physical changes in bottle dimension from procession to procession and within a procession.
A still further advantage of the invention is that the inspection process is carried out using readily available, compact microcomputer and other integrated circuit chips.
Other objects and advangtages of the invention appear hereinafter.